The present invention relates to a method and devices for transmission of broadband electrical signals, for example data and/or video, to a subscriber, particularly a subscriber who has a pre-installed telephone cable. The invention can avoid the need for installation of further drop cables (generally coaxial cables), dedicated to the new data or video service.
As communications technology advances, subscribers are reguesting services in addition to simple telephone service. For example, there is a demand for video and data by cable which requires a high band width for transmission. In this specification any bandwidth greater than that for simple telephone operation (voice band, generally about 4 KHz alalogue amplitude modulated and 64 KHz digital) preferably greater than that for 2,3,4,5,10 or 20 combined public switched telephone signals is referred to as broadband, and includes but is not limited to data and video. In particular, we are concerned with RF, VHF, and UHF signals, preferably of frequency greater than 20, more preferably greater than 30, especially greater than 40 KHz analogue (AM) or greater than 200,300 or 400 KHz digital. In practice we are likely to be concerned with values greater than 30 or 40 MHz, particularly from 47-862 MHz. The invention may also be considered useful for signals having a bandwidth of at least 0.0001, 0.001 or 0.01 times that of NTSC format video.
For some years now broadband signals have been transmitted electrically by coaxial cable. In many installations part of the network is active, which means that amplifiers are provided every few kilometers, and part of the network, namely the drops to individual subscribers running from so-called splitter boxes, are passive. If cable television (CATV), for example, is to be supplied to a subscriber the public right of way and the subscribers garden have to be dug-up and a new, coaxial, line installed in the ground. This is of course very expensive.
We have now discovered that installation of a new cable can be avoided and ordinary telephone cables used instead, particularly pre-installed cables already serving the subscriber.